Don't put someone else before your children and then expect them to be there for you when that person leaves. I see this happen so many times. People, men and women alike, put other people ahead of their own children but then when they need their children, find they are not there.
This happens mostly in broken relationships. One or both parents find other adults in their life and put them before their own kids. I watched my ex husband do this to his own kids. He was with this woman who always came first no matter what. She was more important to him than his own kids. Then when he got ill and she was not there he turned to his kids.
For years his kids were there for him when he needed them but then he would get back with the woman and once again she came first. Not only did she come first but so did her family. He even had more of a relationship with her grandson (a child he called a brat and said he did not like) than he did with his own grandson. All to keep this woman happy.
There finally came a day when his own kids were not there for him when he needed them. They had been there enough, they had been pushed aside for her enough and they had been hurt enough. They couldn't do it anymore. They no longer felt the need to help him because he destroyed their dedication and respect for him.
So if you put someone before your kids don't expect them to put you first later in life. Love and respect work both ways. You have to give to get and can't get unless you give.