You should be honest with this guy about your feelings.
You let him know that you do not like him in a romantic sense.
The last thing that you should do is encourage him.
If you keep allowing him to flirt with you and you respond, he will think that you like him.
As a result, he will keep flirting.
On the other hand, if you simply stay relatively quiet whenever he is making advances, he may still read that as you possibly being shy or playing coy.
You have to actually tell him that you don’t like him romantically.
It has to be very clear to him that this is the case.
He has to know where you are coming from emotionally so that he can either stop his advances or slow down.
If you really like his friend, you should ask yourself why.
What about his friend makes you like him?
Is it merely his physical attractiveness or something more?
You should be certain of this because by attempting to try for his friend, you may cause a rift between the two guys.
Hence, it is better to be certain that your attraction to his friend goes beyond the facetious.
It would be better for all parties if there was some substance behind it.
Perhaps, you like his friend’s intellect or you feel like you have a lot in common with him.
This is a good start.
Again, you want to make sure that if this is something you pursue, your heart is in the right place.
This is crucial.
What often tends to happen is that a person in your position goes after the friend for facetious reasons.
The relationship doesn’t work out as a result and everyone loses.
You lose this guy that you like.
You lose his friend.
The two guys may no longer like each other because you got in the middle.
It all becomes a mess.
If your feelings for his friend were strong and substantive, you will not only have the best chance of having a relationship with him but his friendship with the other guy would also have the best chance of surviving.
If the relationship was based on only the physical, it would be more likely to be short-lived and this doesn’t help anyone.
So, your intentions really have to be clear.
Your task before you do anything else is to make sure that this guy knows that you don’t like him romantically.
When you tell him, be kind and straightforward.
You don’t have to give him a reason but you should be very articulate.
You don’t want him to misconstrue what you are saying and think that he may still have a chance.
He should know that there is no chance.
Your feelings are simply platonic.
After having done this, as I mentioned earlier, you should truly ponder your feelings for his friend.
If those feelings go beyond the basic physical attraction, the relationship that may ensue would have the best chance of surviving.
Hence, being introspective about this and as honest as you can be is helpful.
It gives you more understanding of what is going on and thereby you can act accordingly.