Lost children isn't exactly unknown to Minato and while he doesn't know exactly what happened to Mikoto and the rest of the Uchiha - being inside his son's soul limited severely what he could be aware of and what had managed to filter though - he knows, deep in his gut that it was a horror. Enough did get through and he could piece together a great deal too but not the details. Not the sharp definition of it. So he knew that Mikoto's children had grown up without her and he though no child should grow up without their mother. So his voice is soft and his eyes are calm as he simply says:

"Tell me."