The only comment I could make on your birds would be they are solid whites a splash and a black tailed birds that only specifies colour.
As far as breed they could fall in several different ones and homers come to mind first. Then when it comes to pigeons homers are all I want and think of.
When you say chicks are you referring to young pigeon squabs (if so that does not surprise me).
The only way the squabs may have survived is if you had hand fed them.
The bond between adults and squabs is fragile and sometimes the least disturbance can cause the parents to abandon that clutch of eggs or young.