Any good Apps or services to start a money pool? (me and my brother) (Male21 & Male21)

Ive heard that you shouldn’t get joint accounts with people that you arent married to. But i wanted to know if you guys would consider us an exception to this rule. For context we plan on starting a small joint venture to slightly increase our income. We both have been borrowing money from each other for over five years and we both trust out “credit.” We also share an insurance policy and neither of us missed a payment. Recently i just got out of debt (he helped me out a bit & i paid him back.) Now I’m helping him get his car fixed ($1800) After all of that we plan on pooling our money (while personally saving a bit of course) to start this small venture.

TL;DR – My brother and i want to pool our money to start investing in a small venture. We have a history of sharing finances and we trust each other.