Its not stated for sure, but it is likely they died. Topsy ended up marrying again. (Tria) and Now Cera has a step-mom and step-sister.

I have watched the one where they meet
Petrie's uncle and he wanted to be the leader
So when the the Heard  separated she went with Petrie's uncle
And the people who went with him died!!!they were attacked by sharp touths
And that what happened
Hope this helps