10/07/2009 at 03:00 PM EDT
Amid all the drama surrounding her crumbling marriage, Kate Gosselin
has had one bright spot on the horizon. "Thursday is Cara and Mady’s 9th birthday," Kate, 34, tells PEOPLE, referring to her twins. "That's my focus to get me through the next few days. I'm going to bake a chocolate cake from scratch, and that's going to feel normal and happy."
Now, however, Kate's dreams of a happy birthday for her oldest children seem in doubt. On Wednesday, Jon told ET Online
that Kate is trying to change their joint-custody arrangement so that he is only at their Pennsylvania home from 4 p.m. to 6 p.m. on Thursday, as well as altering their agreement for the weekend – a move Jon claims his tantamount to barring him from the birthday festivities altogether.
"She's trying to prevent me from seeing my kids on Mady and Cara's birthday," he says. "That's like giving her full custody by obeying her. She can't tell me what to do. I'm not going to allow it. I'm just going to stay. I own the house so I can do what I want."
"She's trying to prevent me from seeing my kids on their birthday because she doesn't want to see me," he says. "She doesn't want to hear my apology. She doesn’t want to work things out."