Your brother will able to have sex with his wife or any woman, and since he is circumcised he will experience more pleasure that someone is not circumcised. Since he is circumcised, the head of his penis is more sensative and he will experience great pleasure. I am sure that he is more sensative and receives more pleasure jacking off that someone who is not circumcised. Believe it or not, there is more to marriage than sex.
You can look at it this way. There are several religions that require it and their people keep reproducing so it's quite likely that girls will accept a non intact penis. They surely must work or those religions would have disappeared by now.
There are several benefits to having a foreskin though. One is the inner foreskin is stretch sensitive. They claim it actually has more pleasure nerve endings than all the rest of the penis, so when it's cut off you lose more than half your pleasure center. It's possible to do a circumcision without removing the inner foreskin but the doctors and others who do infant circs don't care about that and it's easier for THEM to just chop off the whole thing. Even when done later in life, most cutees don't know about it and if the cuttors do know THEY don't care. Of all the guys who wrtite in here about circumcision, I have yet to find even one who was informed about his choice of styles.
On the girl's side, the foreskin acts as a buffer between the penis head and the vaginal wall. It keeps the head from scraping against the wall which some girls find unpleasant to downright painful. Of course there are some who like it too. That problem can be overcome by good lubrication or just making the girl believe she's supposed to enjoy the pain to please her lover.
The main benefit of a foreskin is the pleasure it brings to it's owner. It feels great when it stretches as you near the end of the thrust. It protects your glans to retain it's sensitivity so it feels good rubbing against the inside of the vagina. An exposed glans loses most of it's sensitivity and becomes about as sensitive as the skin of your finger.