How about using [Any] type instead of generic types?

import UIKit

struct Team {
    var name: String
    var city: String
    var winPCT: Double = 0.0

    init(name: String, city: String){
        self.name = name
        self.city = city
    }
}

struct Player {
    var name: String
    var height: Double

    init(name: String, height: Double) {
        self.name = name
        self.height = height
    }
}

class StatGroup { 
    var members = [Any]()
    var title: String

    init(title: String, members: [Any]) {
        self.title = title
        self.members = members
    }
}

var blazers = Team(name: "Blazers", city: "Portland")
var nuggets = Team(name: "Nuggets", city: "Denver")

var hoopsUS = StatGroup(title: "NBA West", members: [blazers, nuggets])
hoopsUS.members

var star = Player(name: "Pasan", height: 88)
var benchwarmer = Player(name: "Andrew", height: 66)

var iceFencingUS = StatGroup(title: "Olympic Ice Fencing(US)", members: [star, benchwarmer])
iceFencingUS.members