Sorry, no, he can't, according to the Catholic church rules.
I'll run you through a few facts, give you some points to think about, and let you make up your own mind how you would prefer to deal with the situation.
Firstly, despite common belief, Godparents have absolutely no legal significance or rights regarding the child. It is purely religious, or for many people its a social thing.
Baptisms/christenings are supposed to be done for religious reasons. A Godparents role in the life of the child is supposed to be to ensure that the child is taught and raised properly according to the dogma (rules) of the church. Which, for the Catholic church, can mean that the Godparents should make sure the child is taken to mass every Sunday, goes to Sunday school, doesn't eat red meat on Good Friday, goes to confession, is Communed, Confirmed, and possibly even contributing to the costs of Catholic schooling, etc, etc. Exactly how much responsibility the Godparents take on with this regards is largely between them and the parents. If the parents are doing all that stuff, there's not a lot that the Godparents will need to do. Of course, all this largely depends on how seriously the parents and Godparents take their role and responsibility in this regards.
On the flip side, now days most people have their child baptised/christened for social reasons. This gives parents a way to honour their friends and extended family by giving them a social significance to the child. There is nothing that really needs to be done by the Godparents in this regards except turn up to the ceremony - and even that can sometimes be done by proxy - as the social-only reason holds no responsibility what-so-ever.
For religious reasons, not only would your brother be unable to be the Godparent, being of a totally different religion, but I doubt if he'd want to, given the responsibility involved. I can't see too many Islams taking children to a Catholic Sunday Mass.
For social reasons, given there is no religious responsibility, there's not really any reason why a Godparent can't be of a differing religion; except that if the Church that is baptising/christening the child finds out and refuses to accept them within the ceremony. The question is, who is going to tell them?
Some sections of the Catholic Church now days are also insisting that any parents that want their child baptised with the church attend - I can't remember what it is called, but for all intensive purposes a religious education program - before they will allow the baptism. Some also want Godparents to attend if possible. This can be avoided if you attend church functions regularly and the priest that is baptising your child knows you well, or if you are lucky enough to not live in one of those (can't spell, sounds like di-a-see? so I'll just say...) areas that imposes that little rule.
Socially speaking, all that is unnessary. As an alternative, instead of having your child baptised Catholic, you could instead have a little social ceremony in a neutral place, such as a park or a hired hall, whereby you announce that those that would-be Godparents have a significant role to play in the child's life. This may mean coming up with a different unreligious title (I've heard of Aunt and Uncle being used for example) and defining what that actually means for the family, the would-be Godparents, and the child. You can invent and start your own traditions, your own little rituals, and even blend the concepts of different religious ceremonies together to achieve this. However, be aware that in doing this it can easily offend the sensitivities of people that are very religious if you aren't very careful. You will need to learn about the rituals and why they are used before considering adapting them to your own needs.
You really need to consider why you are going to have your child baptised, why Catholic, and why you want you brother - or anyone else for that matter - to be a Godparent.
I know that in answering your question I've also put you in a position where you need to ask a lot more questions, but they are questions that need to be discussed with your family, those that you would like to be the Godparents, and if you do go with the Catholic church, the priest that will be baptising the child.
Whatever you end up doing, good luck with it.