only lawful relationship is between husband and wife
who are
1) married in orthodox church
2) only do this to have children
3) do it on non-fasting days
4) do it on non-holiday days
for more info, consult your local orthodox priest
p.s. oral, anal, masturbation, abortion, surrogacy, adultery, pedophilia, necrophilia, beastiality, orgies, etc. are all forbidden
p.s. during apocalypse aka now, you're supposed to stay celibate
newborns get chipped in hospitals
newborns are given anti-names aka social security
etc.