"The rules are a little different for marefriends, Soil."
I'll sigh a little bit, and then start doodling in the dirt.
"Alright, so here's how it usually goes. You've got mothers and fathers sharing a bed. Siblings also can share a bed, but past a certain age that is discouraged."
I'll be drawing that out.
"But, before ponies can become mothers and fathers, they are lovers."
I'll put the third group in the drawing.
"Lovers can be two stallions, a stallion and a mare, or two mares. They share a bed with each other because they are in love with each other."
I'll keep scribbling in the dirt.
"However, this does not
mean that all lovers become parents, or get married. Some lovers are just that for a few weeks, maybe a few months, and on rare occasions only a single night. However, if the love between the two ponies is strong enough, they usually end up marrying. Then they become husband and wife."
I'll look over at Soil for a moment.
"Currently, you and Iris are at this stage back here…"
I'll point to the tail-holding stage of marefriend and coltfriend.
"Over time, you two may end up sharing a tent as you start to love each other more. Do you understand?"