Do I have to become my nephew's legal guardian?

This is not legally binding, the family courts, whilst taking your brother in laws wishes into consideration will do what is in the childs best interests and will certainly not place a child with someone who doesn't want them.

However, you need to talk to your brother in law about this.It's not clear whether this is your partners brother or your sisters husband.

Either way, the blood relations need to have a proper chat so that alternative arrangements can be made. How does your partner feel about this?

Same was done to me. I consulted a solicitor and there is no legal obligation on you to become a guardian however if the children were to become orphaned then the emotional pressure on you to look after the children would be high. Its something people shouldn't do without discussion. What for example are the financial arrangements for this ? Have they insured themselves so you will not be under an added financial burden? How would teh additional accomodation needed in a house be managed? Potentially you lose income - how is that handled? Do they expect you to move to the area they currently live in - my brother did , drop your life and take over. People need ot have realistic expectations of what relatives should do with respect to children and what they need to ensure even if the relatives are willing to become guardians.

No, there is no legal obligation for you to be the legal guardian if you do not wish to. I suppose depending on how close your family ties are, they may feel there is a moral obligation.

As has already been suggested you and your partner need to speak with your brother in law and get things sorted.

Sounds like a MAJOR lack of communication. People just don't name the guardian without talking. Did your partner say yes, but not discuss it with you?

No you don't, and your nephew doesn't have to accept you as a guardian either. A court will decide - should this event happen.

if anything like that happened in my family we would all rally round and place the kid or kids in the best place with in the family

you don't turn your back on your kin