DS3 has recently gone into a bed (the bottom bunk) and is sleeping well in it. However, he's taken to climbing up to DS2's bed on the top. It's vertical ladder and very high. Previously this had just been him climbing up in the mornings to play. But last night he climbed up straight after I put him to bed I put him in his bed and he fell asleep.
However later on DS2 woke up and was yelling for a glass of water - waking DS3 up. I went and sorte DS2 out and DS3 got out of bed when I left the room and whinged for a bit. But then he went quiet so I left it.
However this morning I discovered that he'd gone quiet after he'd scaled the ladder and climbed into bed with DS2 and fallen asleep there for the rest of the night
How on earth do I solve this one?