age is only applicable for height based seats. If you have a height based seat, the child MUST be over 15 months. On a weight based seat the age is not taken into account, and they only need to be 9kg but able to sit up for minimum of 30 minutes. I had to look into this when my first was 13 months. She Screamed for entire car journeys rear facing, often up to an hour, once she was so upset she made herself sick which is obviously so dangerous when I couldn’t even see her properly only through the mirror. She then went front facing in an appropriate car seat for her weight and was a peaceful happy car rider. We felt at the time it was safest option for all of us and our day to day journeys were always on 30mph roads so I never was in a situation where I was on a fast motorway (motorways scare me)He was born 29th October (I only know because my son was born the same month). So if we are going by age only he’s not old enough. Not being pedantic but it’s true.