Getting confused

Yesterday, we went to our lovely friends (we'll call them Jane and Tom) for a BBQ. When we arrived with the 3 boys we were introduced to Jane's parents, her brother, his girlfriend and her nephew, a small blond toddler. I was sort of listening to the introductions but at the same time racing after the boys trying to get suncream on and stop them ruining their beautiful house. Jane's parents were telling me how they had looked after their grandson that morning and so I assumed that the toddler belonged to Jane's brother and his girlfriend. So later on I'm making small talk with the girlfriend and saying how she must have enjoyed her lie-in that morning and what did they do with their morning off. Strange looks from her for a good 5 minutes and then I realised that the toddler wasn't hers, he was being looked after by the grandparents as Jane's other sister and husband were at a wedding (I do vaguely remember someone telling me that). How ditzy and dozy. Felt a bit better when our other friend at the BBQ made the same mistake but he was a bit more direct in his questioning of the girlfriend so he didn't have a 5 minute 'weird' conversation. Lesson to myself, I must listen when people are being introduced to me.