I don't think we reincarnate along with most of our family members in any lifetime. I do think we may reincarnate with a few folks more often and they may or may not be family by blood. They may also be family by choice (best mates, partners, etc). Depending on the lifetime.
But I do think that we may see or cross paths with many familiar souls in many lifetimes. These may make up at least of portion of the cast of souls we encounter in our lives.
Only you can say if your mum is a close soulmate. If you feel she is and that she is deeply familiar to you (aside from just being your mum) then you would know best.
Sometimes your family is not close soul family and you do the best you can to get along. It can be hard if there is a degree of dissonance and no driving motivation or bond to build on and mend fences.
Just as sometimes your family is close soul soul family and you do the best you can to get along. It can be hard if there is past life stuff to be worked through and one or the other (or both) are not ready and instead engage more hurtfully and less mindfully. It sounds like it's more the latter here regarding your mum and her temper. My mum had the same problem -- but then so did my cold, detached dad too later -- go figure.
I was the rock in the sand, too. I just said nothing and took it, and mum would calm down. Whilst my dad could rage for ....endlessly really, days on end, if things weren't going well for him.. But then I have never felt as close to him so perhaps that's why it didn't do me in, in the end. Meaning, I always felt mum's soul is closer to me and to my brother, if not in temperance then at least in open-heartedness and emotional generosity. That is, as kids at least we felt she loved us freely and without much resentment. That counts for a lot.
Either of these situations (close or distant soul fam) present challenges and opportunities in the family, really. So either way, whatever you do to develop and mend and grow your relationship with your mum is all good, IMO. Just remember to care for yourself equally...including knowing when to disengage if needed and take time for yourself.
Peace & blessings
7L
__________________
Bound by conventions, people tend to reach for what is easy.
Here we must be unafraid of what is difficult.
For all living beings in nature must unfold in their particular way
and become themselves despite all opposition.
-- Rainer Maria Rilke