@Sazdun
That text he sent that you copied in on your post at 10.27 today is cringeworthy. I feel nauseous just reading it.
As for this bit...
Do I love her? Yes but I cannot explain the type of love it is. She is my friend, I want the best for her, sometimes her choices frustrate me but I am not her husband, her brother so I have to step back and it annoys me at times because I know I could make it better but boundaries and I don't want to step on her man's toes. You know me, I like to fix things if I can. You and I have even talked about this and how we wish we could sort those bits of her life because she is such a great person.
URGH! 
And the fact he says 'I like to fix things, you know me' just makes my toes curl. A married man who has to be the knight-in-shining-armour to another woman who is having issues or problems, (or who he sees as needing support,) is repugnant.
A man who is trying to be Mr Nice Guy to a woman who's a bit vulnerable, or who he SEES as needing help, (when he has got a wife and children at home,) is just one of the worst men to be married to. Because he thinks he is King, and all the wimmin need HIS help to 'fix' them! They need his big manly chest to cry into, and his big manly arms to carry them... 
He does it because it feeds his ego, and because he is often a drip of a man who is a low achiever... so helping an iccle wumman with her life helps him to puff out his chest and look all big and manly and special. No matter how it may hurt his wife and make her feel upset and insecure and hurt. 'Oh, but it's you I love baby....' VOM! pass the sick bucket! 🤢
He sounds like a total twat, and you really need to be looking into ways to get out of this relationship, because once 'Mrs Perfect' decides your DH is just an annoying blob, she will give him a wide berth/ghost him, and he will find another iccle woman to have an emotional affair with.
Sorry @Sazdun but he sounds pathetic. You - and your children - deserve better.