I've never had a problem with being in love with more than one pair of shoes. Most of my shoes are Birkenstock, but there are a few other brands. I need more than one pair of shoes to satisfy different needs that I have. I got great deals online for most of them, but some I paid full price for because I needed that style and just couldn't find it at a discount.
None of my shoes have ever been jealous when a new addition is made to our shoe-family, although I have discovered certain redundancies after the fact and re-directed some pairs to other folks either through my circle of friends or via eBay.
My relationship(s) with my shoes are very distinctly individual, and of course my love for one pair in no way diminishes the total amount of love I have to offer to as many shoes as will accept it.
That's about all I have to say about that for now. Thank you RP for bringing up this topic in its own thread!