Hello,
For "family" there is familia, but most of the time it didn't actually mean exactly what we mean today by "family", but the whole household including all slaves etc, even if it sometimes meant "family" as well. Now I think it might not be the best word to use here; as you're speaking specifically of your father, mother and sister, I think this would have been expressed more naturally in Latin by proximi, that is literally "the closest ones".
My family, my strength:
Proximi mei, mea fortitudo
Familia mea, mea fortitudo - or robur meum, which could be "strength" or "source of strength".
My strength comes from my family:
Fortitudo mea e(x) proximis meis venit
Fortitudo mea e(x) familia mea venit
Or fortitudo mihi e(x) proximis meis/familia mea venit, which would be literally "strength comes to me from my family".
Now I'm not completely sure that "strength comes from..." is very natural Latin - but I may be wrong, you can wait for what others say. Now if you choose the version with robur for the first phrase, the idea may be somewhat included in it, as it can mean "source of strength", so where it comes from...
My family, my foundation:
Proximi mei, meum fundamentum
Familia mea, meum fundamentum