two masters:

-- 192.168.126.128 mysql 5.6.12
-- 192.168.126.129 mysql 5.6.12

slave :

-- 192.168.126.130 MariaDB 10.0

from one master machine create new db and insert one record:

23:44:55 (none)> show master status
    -> ;
+------------------+----------+--------------+------------------+-------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000004 |      544 |              |                  |                   |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.07 sec)

23:45:51 (none)> create database mariatest1;
Query OK, 1 row affected (0.21 sec)

23:50:14 (none)> use mariatest1;
Database changed
23:52:16 mariatest1> create table liuyang (id bigint);
Query OK, 0 rows affected (1.42 sec)

23:52:30 mariatest1> 
23:52:31 mariatest1> insert into liuyang values (1);
Query OK, 1 row affected (0.17 sec)

23:52:37 mariatest1> commit;
Query OK, 0 rows affected (0.01 sec)

from secoend master machine  create new db and insert one record:

23:47:23 (none)> show master status\G
*************************** 1. row ***************************
             File: mysql-bin.000005
         Position: 550
     Binlog_Do_DB: 
 Binlog_Ignore_DB: 
Executed_Gtid_Set: 
1 row in set (0.00 sec)

23:47:29 (none)> create database mariatest2;
Query OK, 1 row affected (0.13 sec)

23:50:27 (none)> use mariatest2;
Database changed
23:52:48 mariatest2> create table liuyang (id int);
Query OK, 0 rows affected (0.65 sec)

23:53:43 mariatest2> insert into liuyang values (1);
Query OK, 1 row affected (0.12 sec)

23:53:55 mariatest2> commit;
Query OK, 0 rows affected (0.00 sec)

change Mariadb slave connect to these two masters:

MariaDB [(none)]> SET @@default_master_connection='t1';
Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> CHANGE MASTER 't1' TO MASTER_HOST = '192.168.126.128', MASTER_USER = 'repluser', MASTER_PASSWORD = 'rep', MASTER_PORT = 3333 ,MASTER_LOG_FILE = 'mysql-bin.000005',MASTER_LOG_POS = 550;
Query OK, 0 rows affected (0.01 sec)

MariaDB [(none)]> SET @@default_master_connection='t2';
Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> CHANGE MASTER 't2' TO MASTER_HOST = '192.168.126.129', MASTER_USER = 'repluser', MASTER_PASSWORD = 'rep', MASTER_PORT = 3333 ,MASTER_LOG_FILE = 'mysql-bin.000004',MASTER_LOG_POS = 544;
Query OK, 0 rows affected (0.01 sec)

[mysql@mariadb ~]$ mysql  --socket=/mysql3333/mysql/data/mysql.sock
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 13
Server version: 10.0.10-MariaDB-log MariaDB Server

Copyright (c) 2000, 2014, Oracle, SkySQL Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> START ALL SLAVES;
Query OK, 0 rows affected, 1 warning (0.00 sec)

MariaDB [(none)]> 
MariaDB [(none)]> show slave status
    -> \G;
Empty set (0.00 sec)

ERROR: No query specified

MariaDB [(none)]> show slave status \G;
Empty set (0.00 sec)

ERROR: No query specified

MariaDB [(none)]> show slave 'T1' status \G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.126.128
                  Master_User: repluser
                  Master_Port: 3333
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000005
          Read_Master_Log_Pos: 550
               Relay_Log_File: GSS-01-relay-bin-t1.000002
                Relay_Log_Pos: 407
        Relay_Master_Log_File: mysql-bin.000005
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 550
              Relay_Log_Space: 708
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 6
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
                   Using_Gtid: No
                  Gtid_IO_Pos: 
1 row in set (0.00 sec)

ERROR: No query specified

MariaDB [(none)]> show slave 'T2' status \G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.126.129
                  Master_User: repluser
                  Master_Port: 3333
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000004
          Read_Master_Log_Pos: 544
               Relay_Log_File: GSS-01-relay-bin-t2.000002
                Relay_Log_Pos: 407
        Relay_Master_Log_File: mysql-bin.000004
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 544
              Relay_Log_Space: 708
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 5
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
                   Using_Gtid: No
                  Gtid_IO_Pos: 
1 row in set (0.00 sec)

ERROR: No query specified

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mariatest1         |
| mariatest2         |
| mysql              |
| performance_schema |
| test               |
+--------------------+
6 rows in set (0.06 sec)

MariaDB [(none)]> 
MariaDB [(none)]> select * from mariatest1.liuyang;
+------+
| id   |
+------+
|    1 |
+------+
1 row in set (0.00 sec)

MariaDB [(none)]> select * from mariatest2.liuyang;
+------+
| id   |
+------+
|    1 |
+------+
1 row in set (0.00 sec)