Long version:Actually yes there is one case we know of a child being a guardian he may not have known he was but he was one I’m talking about Shin Malphur he was a child that would grow up to kill Dredgen Yor and be the first Gunslinger now the fact that Shin could summon a Golden Gun means he has enough light to be considered a Guardian so there’s no evidence to believe he didn’t have this light as a child Short version: Shin Malphur was a Guardian child because he could summon Golden Gun