Yes. The whole mission of Christ was to save and change people like your little brother.
It's a touchy subject, because so often people will develop a self-protective delusion that they're "born this way", but even if that were true (which I don't believe), in Christ we are to born again anyways, and through the process of confession, repentance, prayer, and study, victory over sin through Christ is possible.
We're never maneuvered into situations where sin is inevitable, we can always choose the way of Christ.
1 Cor. 10:13
13 There hath no temptation taken you but such as is common to man: but God is faithful, who will not suffer you to be tempted above that ye are able; but will with the temptation also make a way to escape, that ye may be able to bear it.
Keep praying for your brother of course, and be a good witness, it might take years and years, but it will have to be your brother's choice ultimately.
Remember to be generous and kind, but never compromise truth or be a pushover about these issues. Too often people are either permissive or they're bullies ‒ cursing at and tormenting brainwashed sinners is not the way we are to engage fellow man.
Colossians 3:8 - But now ye also put off all these; anger, wrath, malice, blasphemy, filthy communication out of your mouth.
Ephesians 4:29 - Let no corrupt communication proceed out of your mouth, but that which is good to the use of edifying, that it may minister grace unto the hearers.
James 1:26 - If any man among you seem to be religious, and bridleth not his tongue, but deceiveth his own heart, this man's religion is vain.
>Testimony of former gay
youtube.com/watch?v=IkDi40UBgmA
>analysis of gay agenda
youtube.com/watch?v=DaR7-aW2LL0