Technically Tir does speak in the game, because whenever you're given dialogue options they're the exact sentences that he'll say rather than just "Yes/No" stuff.
maybe because they both have their own cameo appearance as secret characters, Tir was a secret playable character while Red was a secret boss also they are both protagonist of the first game of their own series.
Wouldn't the most obvious connection be that in both games you're supposed to catch/recruit/gather an absurd number of followers? I think in the first Suikoden game you needed all 108 to get the best ending.