My son had contact with birth mum initially, but it only happened 2 or 3 times. She kept cancelling at the last minute, which was very unsettling for my son. I do understand it was difficult for her too, but it created unnecessary emotional turmoil at our end. So contact fizzled out.
We did talk about his birth family if he wanted to.
A couple of years ago, when he was 20, he wanted to get in touch and we helped him make contact. But we did warn him it was a very dysfunctional family then, and could still be now.
Initially it all went well, he stayed over with birth mother and a younger siblings a few times. That was very hard for me, but he was very clear we were mum and dad and his home was with us. But within a couple of months the gloss had worn off. I think he is still in touch with a younger sibling, but he basically said if he had been left in that environment he would either be dead, a junky or in prison.
And the adoption support fund was totally useless for us. Refused to pay a penny towards any of the support we paid for as they said "it wasn't directly related to the adoption". If course it bloody well was, it was all the trauma he carried from being left in totally unsuitable conditions for 15 months while mum was given chance after chance to sort herself out. But I didn't have the energy to argue.