A while ago I fell in love with a woman who had children, and was technically still married. She had been separated for years at this point (there was physical, mental, emotional, and sexual abuse) with full intention of divorce, but financial problems held her back. I stepped into the picture and tried showing up to the children’s life as a parent as best I could. I had a lot of my own issues, it’s a huge task to try to take on, but I’m curious what Islam says about this kind of situation; step-parents and separation.
It is very noble that you want to be a stepfather to these children. Prophet Muhammad (sa) had done the same thing. He proposed marriage to a widow with young children. The widow’s name was Hind bint Abi Umayya, known as Umm Salamah. It was the Prophet’s intention to support the widow and her family, but Hind wanted to make sure, so she sent a message to him, saying, ‘I have young children.’ The Prophet’s response to her was, ‘Your family is my family.’
Many of the Prophet’s companions had done the same things.
Parenting is holy work, and it requires knowledge, so make sure to continually increase your knowledge of healthy parenting.
In addition, caring for a woman and children who had experienced and/or witnessed abuse requires professional help, so make sure they have access to that. Also, do not forget to give yourself the self-care you need to renew your emotional and spiritual energy and do not get burnt out or drained.