Example: rows 9 and 10 in the theatre are ??? rows.
Alternatively: rows 9 an 10 are ???-ly adjacent (while seats B and C are laterally adjacent).
There are words like subsequent, consecutive, etc., which have a somewhat temporal flavour, or at the very least hint at a sequential context (both are cognates of sequor, after all). But what's a good word choice for a strictly spatial context: an object behind/in front of another?
Clarification: I am a quasi-native speaker specifically curious as to why such a word seems so elusive, and equally as interested whether such a word exists in other languages. If there's no such thing, I'll accept that as an answer too.