Blackbird Fledglings

Sometime ago I posted a couple of pics of Bert and one of his kids. I haven't seen them for a while. Just the other week I spotted a Blackbird chick on the grass. It went rummaging in the flower borders and eventually the rockery. To my surprise when it went to the rockery I caught a glimpse of another chick at the rear. Are they brothers, sisters, brother and sister or not related at all. Chances are they are from the same brood but there was no sign of either parent. Maybe they are having their second brood of the season. Hopefully they will bring more of their family . First pic was the first one I noticed.