If my twin flame is happy with his family? Do I still have a chance?
True twin flames were bonded together before they were born. For eternity. You are identical twin flames. You are reincarnations of each other. You share the same soul.
Because this bond existed before you were born, any relationship here on Earth is on a lower level than a twin flame bond.
The hierarchy of relationships puts twin flames at the very top, soulmates and karmic relationships are below, including marriage with soulmates and karmics.
A true twin flame usually won't be truly happy in a relationship outside of their twin. If it appears that way, either she is hiding it, or denying it for outward appearances, or she is not your true twin flame.
Not everyone has one, it's extremely rare. Many twin flames have children and are married. However, for true twin flames, marriage with a soul mate or karmic will not be as fulfilling as with the twin flame.
And yet, it's best for any twin flame not to interfere in their twin's marriage. If this is your true twin flame, the marriage will take care of itself. The spouse will leave on their own, or the twin will leave on their own, or the Divine/God will step in and take care of it.
If this is your true twin flame, you don't have to worry about it. This is not your challenge.
If your twin truly has a happy family, then either that's what he wants to come up to you and the world, or he's not a real twin flame. Either way, don't interfere.