Yesterday I found Arwel on his back in his cot (he sleeps on his belly) and I was so surprised but than it clicked that Tristi did the same, he turned once before he was 3 months old and than really started to roll when he was 4 months. We will see.
Also another early thing was with Tristan is his teething, first one broke through also at 4 moths. Well Arwel will be earlier in that I'm sure, he's got all rosy cheeks and you can see the teeth getting whiter and whiter.
We can see that he will be an active one, not a slow one like Elen (who also caught up since).
Here is a video of Arwel being hyper. he just wants to go :)