After her husband left and Alex left to go on his journey Alex's mother no longer had the heart to remain in Saffron and so she bought a small ranch where she raises pokemon and continues her breeding business. This is where Alex stores the rest of his pokemon.
Geist(Chabelere)(β)- Caught as a Litwick he was the first ghost type he caught in Unova. For quite a bit Geist was an important member of the team but eventually Alex's stubbornness and refusal to lose pushed the pokemon to hard which resulted in Gesit getting terribly hurt in a battle gone wrong. Alex couldn't forgive himself and retired the pokemon from battling.
Set(Cofagrius)(β)-Caught in Unova as he was trying to complete his team. Set was independent, strong, and far to battle hungry. Even Alex found him difficult to control in battle as he would often not listen to commands and would often take the fight to dangerous levels Alex retired the Pokemon from battle. Originally intending to simply release him to the wild believing him to dangerous to leave on the ranch his mother persuaded him otherwise claiming she would be able to handle whatever the pokemon could dish out. To hear her talk she has apparently succeeded as he is much better behaved now.
Letty(Golett)(β)-Alex stumbled upon Letty one night he was sleeping after she woke him up looking through his things. He caught her then and there. He was delighted to find another ghost type but quickly decided against using the timid and sweet pokemon in battle.
Ronin(Aegislash)(β)-Much like Geist Ronin was the first ghost type to join the team while Alex was in Kalos. For a time he battled admirably but eventually found that he didn't enjoy battling all that much and so requested specifically to be sent to the ranch to live out the rest of his days peacefully, a request which Alex reluctantly obliged.
Revenant(Pumpkaboo)(β)-Along with Willow Revenant was caught when he was trying to find a replacement for Ronin. Eventually it was decided that Willow was the better choice for battling as much like Letty his caring and sweet personality was ill suited for it.