Can you have profssional relationships with family?

[BlueFishWonder]

Being driven a bit mad at the moment. I work with my brother. When the business was set up I had the option of being a full partner. As I was pregnant at the time I decided that wasn't for me, but when they offered a full time position employed I accepted. This is a dream job which I love and I know I am very good at. I started a new section of the business from scratch, I was given a lot of freedom and have built it up to being a really successful enterprise and know I've done this well. My brother appears to not be able to accept this, he is determined to put the boot in and cause arguements when there is no reason too, if I challenge etc it immediately turns into 'well I'm the boss', even though he and I know he knows very little about the area I am running and I was brought in as the specialist. I love my bother dearly outside of work but he is driving me crazy internally, he seems to have little to no respect for me and uses me as his personal punch bag. I think he has being having a tough time in personal life, and feel like I get the brunt of it elsewhere.
He will play the status card and flex his muscles at every opportunity, even to the detriment of the business. This has been relatively recent and up to a few months ago we worked brilliantly together so I don't know what has changed. I really do love my job, I don't want to leave and I am so proud of what I have achieved, I love the team I work with as well just feel really hindered by this aspect! But saying that my relationship with my brother and his family is more important to me than my work.
Was I foolish to think we could have a professional relationship inside work and a personal one outside?

He sounds like he has very low self esteem?

Is he sensible enough to have a mature discussion about how this situation is not beneficial to the business.

Is this db older or younger? Why not broach the subject over dinner/something away from the work environment and voice your concerns? Do you think that might work?

DB is older, I wonder if it is a self esteem thing, I feel 'put in my place' alot! I would hope he would have a conversation but he is very status driven and anything threatening that he dislikes. He won't admit to failures or doing things wrong and in our entire relationship I think I can remember him apologising only once.
He can be a really difficult bugger and I feel I bend over backwards for him to defend him, support him etc, etc. He has also done alot for me over the years, he is quite a it older and supported me alot through later teenager years and early twenties. We've always been really close, but on saying that he will be brutal in who he cuts out of his life and isn't very good at forming or holding down relationships.
If I was in any other job I wouldn't accept it from another boss, I feel am more loyal and more tolerant because of the relationship. However I will argue back a lot quicker as well.