You need to look at this logically OP
Can you provide financially for these kids long term. How will this impact your financial future, will you need to take days off work if DC are sick or covering school holidays.
Can you cope mentally, you have decided not to have children yourself so how are you going to be equipped to parent two likely traumatized DC.
Can you protect yourself from the parents of these DC, will they cause problems for you.
What emotional support do you have, do you have a partner that can support you, any other family members that can support you and allow you to have breaks by taking the DC for weekends or on school holidays.
I would not expect any support from SS if you take these DC. A family member of mine was guilted into taking on a troubled grandchild against all their own instincts. Pressured as he was family, it was only right to take in GC, how could you let him go into care. This was six months ago, after countless pleas for help from SS, endless visits to the home by cops to try to wrangle this kid, finally last week this 13 year old kid beat his grandmother so badly she ended up in hospital. The grandparents can't take any more, he now has to go into care which is exactly where he should have been placed six months ago, but now his relationship with GP is completely fractured. Hopefully now he can get the expert care he needs to heal his trauma but I don't know if there's any way back for the family relationships.
Please think carefully and realistically about what you can cope with, there's no shame in not being the best resource for the DC right now.