I might be misunderstanding your question and posts. But I think you are asking two slightly different things:
- firstly, should you leave money to your families (parents/ siblings) in your will as well as to your children?
- secondly, who should you place as guardian(s) for children if you die?
Apologies, if I’ve misunderstood and you only want to leave money to a relative if they are going to act as guardian.
I think it matters how much you will have to leave. I think from what you say, that you are talking about a very ordinary situation here, and so this isn’t about some incredibly fortunate couple with millions in the bank who want to make their family’s lives better if they die. You have a mortgage and life insurance and perhaps some savings and investments.
In that situation, most people leave everything to their children. Maybe the odd bequest to charity or a certain treasured possession to a sibling or something.
It would be very unusual to leave money to siblings and particularly odd to leave it to parents. These are grown up people earning their own money, living their own lives, and not (as far as I can see) currently financially supported by you.
Now, if you didn’t have children, it would be a completely different matter, but you do.
Why would either of you want to take money away from your children to benefit their grandparents and aunts/uncles? Unless you have millions to leave, it seems a strange thing to be considering. Especially if your children are young enough to require guardianship if you died now. You’ll surely want them, and so their guardians, to have access to funds to support their futures (living costs, university, a start in life afterwards), and not use that so that your parents and siblings can have, what? A bit of cash for a holiday or something???
Absolutely, you need to sort out a plan for who will take the children if you both died. That’s always incredibly hard, but you don’t need to leave money to that person/people, you have a will that means your children and their guardians could use money, in trust, to fund their expenses. You absolutely do not want to pass money you want used to benefit your children onto someone else with the hope or expectation that they would do the right thing with it. You tie it up to your children.
Edit: to say that I keep using ‘you’, as a collective for you and your husband, but I think I mean, ‘why on earth would your husband want to…’ in the main.