My husband is the second youngest of seven kids. On multiple occasions, I've asked his mom, "What was Mike like as a baby? When did he walk? Did he cry a lot? How did he sleep?"
Always - my mother-in-law looks at me, laughs, waves her arms, and clearly explains that after seven kids and 30+ years - she - does - not - remember - anything. The most I can get from my in-laws about their memory of my husband was that he was "the fat one."