sikh the religion, please help?

It is not a Sikh related issue. Religion dictates faithfulness to the partner. So this person is breaking the rule. Like in all other religions, not everyone follow the rules. It is a social issue. It depends upon, how strong minded your friend is and how he is tied with you? Life is not lust. After living together 2-3 years, in normal families argueing start appear. If someone leaves his/her family for this reason and opts to choose another partner, he will face the same situation in less than 2 years because it is the same person who is choosing a partner and living. In a triditional sikh house, every type of pressure will be used, parents, relatives, sikh monks etc to avoid breakage. That is the reason there are negligible number of divorces. I have seen splits in sikhs too and almost every member of community will talk about them because they are so rare.

Are you saying you're male Sikh friend wants to leave his wife for a young western girl?

I don't think it would be looked upon as a good thing to do, i'm pretty sure family will be strongly apposed, I have a Sikh friend and she's got a white British boyfriend, she's had to keep it a secret from her parents for the past year for fear of what her parents would say.

I know male and female can be treated differently but i'm pretty sure no one would be happy with this situation. But for the good of your friend, and if the situation calls for it I don't believe that religion should at all restrict your life, should do what's in your heart, but then again I'm not a Sikh and there could be a danger he'd fall out with plenty of his family over an issue like this.

Hope it works out.