Following Final Fantasy VII, there are similar storylines between Cloud/Aerith and the other main couples in VIII, IX, and X.
Their love story was never complete. It was an attempt to make FFVIII the love story. Maybe it was because Square regreted ending FFVII without Cloud and Aerith getting together, so they made connections between Cloud x Aerith, Squall x Rinoa, Zidane x Garnet, and Tidus x Yuna, in my opinion.
But there were always two certain other couples in the series that may have inspired Cloud and Aerith; Cecil x Rosa & Locke x Celes. In both FFIV and FFVI there were scenes that are similar to those in FFVII. And maybe they just wanted to attempt that in VII, but never got the chance to complete it.