Blackbird and babies

I have a blackbird with three babies in the nest just by my backdoor. The father was killed by an hark just as she had laid the eggs.
The babies have just hatched and she is busy feeding them,

When they first starting building the nest, there was another male blackbird that attacked the nest and it landed up dropping on the floor and they built another one.

Since the father was killed, the other blackbird keeps flying into the tree and nest when the mother is out looking for food. Each time I go out to look, it flies out the other side of the tree. Now I have seen it flying in when she is off getting food for the young.

Will it kill the babies or try to damage the nest? It does not go in when the mother is on the nest at all.

Many thanks for your help.