This is also something that you will have to accept.
A widower has made a life with someone else and he has been through a wedding, in-laws and has created a family already, so before you start to get serious you need to discuss a future and what you would like before you or he can fully commit.A widower is even more of a challenge as with everything in life, time is the only thing that can heel wounds.If they have been used to doing things in a certain way, it is extremely difficult to change bad habits or create new rules.As partners you need to know what is expected from each of you and the children in order to build a life and a home together.Grandparents and siblings of your boyfriends late wife will want to stay in contact and there is no option here but to accept it.
Memories of their mother will be important to them and your boyfriend or husband will want to share these with his children so that they will always remember who bore them.
In the beginning, they might be a little moody and cry but this is because they are missing the nurturing, which you cannot give them but as a women, we all have a maternal instinct and all you will need to do, is give lots and lots of love.
Patience is something that you will need a lot of and as long as you try your best to give them all the love that you can, then you will be fine.
You need to let them know that they can turn to you at anytime for any reason, to speak about their hurt.
It is extremely difficult to take on children that have already been raised by a mom and dad.
They will resent you in some way and if not now, later there will come a time where they will hate you and wish for their real mom to be there, instead of you.