Here's Sweetie Belle with her younger children, whom she had with Rumble. These two are closer in age with the rest of the CMC kids.

Echo Belle is her son, and the eldest of the two. His passion follows his mother as a singer, but he can be rather shy at first. He loves hanging out with Aunt Rarity, and his wardrobe is made up almost entirely of Rarity Originals.

Bromeliad Breeze is Sweeties youngest daughter, her passion is plants but she leans more towards a scientific aspect on them, she will breed them to propegate different growth styles and mutations, she loves seeing a flower with a new feature she hasn't seen before in her collection, and if somepony falls in love with one of her flowers she is happy to snip it off and let them take it.

I might elaborate more on these guys in the future, but there isn't a big story on how these two got together, they had some chemisty as kids and Rumble got closer to her after Sweetie regained her senses following the Spike incident and raising Smokey.