My niece is going to get married soon and her husband’s family want to have music and songs in the wedding ceremony. Can I go just to sit with my niece or it’s haram.

It is Haraam for you to go and sit with your niece in the wedding ceremony knowing that music will be played. In fact, it may even be your religious duty before Allah to practice “Nah-y ‘An-el-Munkar” – which means to forbid evil – by reminding the future in-laws of your niece of the Haraam nature of music, and they should therefore refrain from allowing music to be played during the wedding ceremony. If they persist on doing so, you could arrange with them that music be stopped for a period of time – say half an hour – so that you, and others like you, could participate in the wedding ceremony for that period and then leave.