In my point of view, of Ran´s parents, I think that although Kogoro is always lazy, watching Yoko-chan, drinkink beer and playing Mahjong up late, he loves Ran, because in some episodes when Ran is in danger he always had to get to her even if he could get hurt or being killed. I can´t say anything about Eri because there aren´t many episodes invloving Ran-Eri relationship but, I think she loves her also because of the fact that in
. About the 20 year-old marriage, I can´t say anything neither, beacause we really don´t know what happened in Ran´s childhood.
Now, Shinihi-his parents realationship. Not much to say, not many epiodes with Yusaku and Yukiko, but it can be sai that Yusaku and Yukiko don´t love Shinichi beacause thay are always travelling and don´t get worried about Shinichi´s life. However there are some episodes saying that there is also some love:
Thay 20 year-old marriage, nothing to say. Well, not counting the two parts episode od Shinichi and Ran Childhhood adventure, because it doesn´t show any realtionship. Who knows, maybe Gosho will come up with episodes relating to REAL Shinichi and Ran childhood and the realtionship with thier respective parents.
Note that this is my point of view, if anyone wants to say anything against it, feel free.