DD1 was a good sleeper since she was 4 mo. She had good sleep routine and fell asleep by herself, consistently slept through night, in her own bedroom. We moved 3 times since then, her sleeping place changed from crib, to toddler bed, to twin bed. She never had a problem, or transitioned quickly.
DD2 was born 4 months ago. DD1 had little hard feelings. Her sleep wasn't affected. DD1 started to go to a new preschool 3 months ago, Her sleep wasn't affected either. She isn't sick recently.
However, since about 1 week ago, DD1 started to come out of her room for us during the night. She normally sleeps 730pm-630/700am. The past week, she usually wakes around 1am, comes to us saying that she cannot find her lovey/she is not able to fall asleep/she wants to go potty (she has a potty in her room and she's been able to go herself since 6 months ago) and other various reasons.
I'm sleeping in DD2's room and most of the time it's DH who takes care of DD1 when she comes out. He first tried comforting her and sent her back to her bed. Then she came out twice instead of once. Now DH becomes angry and timeout DD1 when she comes out during the night. It doesn't work.
What might be the cause? What shall we do to stop it? DD1 has waken up DD2 and made everyone very tired the whole night. Please help~