You need to ask yourself what you want to gain from this. In truth they’re not going to be siblings in the true sense of the word. They’re siblings by birth only, but you don’t have a sibling relationship, iyswim.
My DP has a sister who was adopted at birth. Slightly different situation but she and all the other children were removed because of abuse. The other children were abused and raised in foster care whereas she was actually removed and placed for adoption at birth. Fast forward to when the DC were older, and they regained contact with each other with the exception of one who wants nothing to do with them. However, they also had some contact with the sibling who had been adopted, and DP’s brother especially was very drawn to this sibling relationship. In truth they fell out and were actually completely NC for around the last six or seven years, but apparently had a bit of contact in the past couple of months. And then she died very suddenly, and the brother has re-written the relationship as one of siblings who were incredibly close, who would be spending all their time together, going on holidays, how he was uncle to her children and so on and so forth. But the truth is far, far removed from that, and as a result it has almost broken him.
Bear in mind that you have grown up in a different environment, and they are unaware of your existence even. Finding out that you exist and then finding out that their mother wants nothing to do with you is going to potentially re-frame the thoughts and feelings they have around their own upbringing and their mother, and there is no knowing that they will even want to know, or that they’ll even believe you are who you say you are let alone want to have any kind of relationship with you, especially if this compromises the relationship they have with their mum.
I sympathise entirely with your wish to want to get to know them, but sadly these kinds of situations almost never turn out the way we hope they will.