Family businesses can be very rewarding and a living hell at times!
I actually started a Heating/Cooling business when I was 24 years old and a year later Dad joined in as a 50/50 partner. We had worked together in the past for the same employer,I started working summers when I was 14 years old where Dad worked.
There were a lot of strains through the 21 years we worked together in our business. I was more business orientated,so naturally I was the estimator,billing,accounts payable,phone secretary,and measured and lined out every job for those 21 years. He was much more relaxed than I,sometimes even the I don't give a F*^# attitude?? and at the same time telling me I was too particular and tried too hard??....So yeah lots of stress!!
What we did to maintain our Father Son relationship through all of those years? We did a lot of hunting,fishing,shooting together like we always did way before the business.
My little bit of advice try to find something you both enjoy doing and while doing that leave the work at the work place for those times,it really helped us through the years.