A Demonic Being Followed My Family Across The Continent

My cousins have been dealing with freaky things happening from the very beginning. They first lived in an old farmhouse where mildly scary things happened semi-regularly, lights flickering, footsteps, etc. At this point it was just my aunt, uncle and their oldest child who was just a toddler.

They then built a brand new house in a quiet part of town and that's when things actually got worse. By the time their oldest daughter was a young teen, they had 3 more children, who were all experiencing now terrifying things. Doors were slamming shut, they could hear whispering almost every night all around the house and the oldest daughter was seeing a large man with bird-like feet and huge wings. She saw him on a couple of occasions just briefly but described him as completely black without a face or any features, standing at the foot of her bed in the middle of the night before it disappeared.

This family is very close with God, they attend church every Sunday and have a very strong faith. But the family soon discovered this oldest daughter had been experimenting with Ouija boards and other dark things and they packed up the family and moved to Central America for a year as a sort of "fresh start" in hopes that they could return one with all this left in the past.

While they were in Central America, however, things hit their peak. The sound of furniture scraping along the floors (my cousin described it like someone was pushing a bed from one end of the bedroom to the other over and over in the upstairs bedroom above her) happened often and they had horrible smells in their home like rotting meat.

A couple of times in the middle of the night they heard very very loud whispering (she said it was loud enough to hear clearly but sounded breathy and hushed) outside their windows, speaking a strange language. Their dad speaks Spanish and although this was in a Spanish town her father confirmed that the voices were not speaking Spanish or anything similar, and there was no one outside when he investigated.

One daughter also had a door slam in her face. She was terrified and began screaming and attempted to run to her sisters bedroom for help but as she was doing so, simultaneously every single door in the house slammed shut. They didn't lock so she was able to simply open them but it was obviously quite terrifying. They had a pastor come to their home and bless it, although they said nothing changed.

After a few months of living there, the youngest daughter in the family developed a severe illness and had to be promptly flown back to Canada for treatment. After they arrived back in Canada, strange things continued happening but not quite as violent or often, just strange things off and on. Their motion-detected garbage lid lifts by itself and lights appear on in the middle of the night, etc. That was just about 10 years ago and now things are starting to get very very bad again.

The youngest child of the family, the only son, went to university and in the meantime nothing even remotely strange happened in the home. He just returned from school about 2 weeks ago and it seems like it has come back with him. He says he saw the dark bird-like man in his room at night and again on the stairs in the same week. He also says it speaks to him and tells him to do terrible things. He has never been involved in any dark practices and has a very close relationship with God so we don't know why it would attach itself to him or if that's even what is going on.

I'm very close with this family and have witnessed a lot of these things first-hand when staying at their home but I have no clue how to help or where to start. These experiences are absolutely terrifying for the whole family and after 25 years of this happening, we really want answers or even just opinions if you think you have ideas of what this could be? Why it would be doing this? Or how we could go about attempting to stop this?