How did your partner's ex react when told that you were expecting? Either from DP or your DSC?
With our first child (DD) Dp told his ex himself. He thought it was more respectful if he told her. He obviously told his two other daughters also but wanted to be respectful to mum. We've gone on to have a DS together too but since he's come along things have really soured on her side. She refuses to acknowledge her daughters and my DD and DS are related. DP's DD2 called DS a 'runt' the other day. When DP asked where she got that from she told him it's what her mum calls him.
Needless to say DP was soon having words with the ex, which seems to have soured things even more.
She is constantly reminding DP that my two boys from a previous relationship are not his and he is dad to their daughters first and foremost before he thinks of trying to parent mine. Which I can honestly say I've never expected DP to do. They have a dad of their own.