Parrots have not been bred down for thousands of generations to just automatically "like" humans like dogs and cats. They are at most 2-3 generations out of the wild. They are essentially wild animals (even if born in captivity) who have a strong prey drive (fight or flight), the asset of flight and large, powerful beaks designed to hollow out trees, rip open thick skinned fruits and crack nuts. Your particular birds have endured the mental trauma of being locked in a cage all day for many years. Likely after they were lavished with love and attention for some time (before the novelty for the prior owners wore off), then locked up for no reason without adequate diet or mental stimulation. Put yourself in their shoes and imagine how YOU would feel towards humans after that? Probably rather aggressive and angry.
This will take time and effort on your part. You can expect to be bit, several times, with blood drawn. Again, parrots are not feathered dogs and they do bite from time to time as a matter of normal behavior (even more viciously/frequently when they do not trust you). I would not let them interact with your children yet, as they are liable to bite them too. My bird was also a cage-case, locked in a tiny crate for many years because he "misbehaved" (i.e. he acted like a parrot...shocking!). He was vicious and feral when we got him. He bit me and my husband (me more than my husband

) many times, some of the bites were pretty severe too. It took a solid year to get him semi-tame and several years to completely turn his behavior around and earn his full trust. He is VERY bonded to us now and as you can see in my profile pic, a real sweetheart of a bird who loves his kisses more than anything came out of a once "evil" bird. Time, patience, understanding is what takes birds from feral to friendly.
I would suggest to start with you sit by their cages and read or talk softly to them. If the come over, reward them with a small treat and verbal praise. Better yet, take a bowl of fruit over and start eating, then share some. Food is a BIG trust builder with birds. Sharing "your" food is a way to communicate that you want to welcome them into your "flock". Once you've started making some headway with that and see they are starting to become more happy to see you (expect a few weeks, maybe sooner maybe longer though) then look into target training. Lots of free youtube videos explaining the concept and it's a great tool to work with vicious rehomes to create a way of communicating with your bird and building mutual trust

Don't despair this soon after getting them! PLEANTY of people have had their birds make total behavioral turnarounds and all it takes is patience, love and a true commitment to being the birds forever home (i.e. not giving up on them because they are difficult). Best of luck.