Others have already said but its not difficult, Marianne is the eldest, daughter of the first queen. But like others said a male would typically supersede succession, so him being born second wouldn't change the king and evil queen's perception of him being the successor, until they abandoned him due to lack of magic. Raius is Haruto's full blood brother and the evil queen is also his mom.
Char's exact relationship isn't known for sure, but I do think its eluded that either her mother or father are related to the royal family, making her in line of succession, and likely some sort of cousin to Haruto and the other two.
More important question, 2nd season of the show when?
And if someone wants the full monty of suffix / endings, just watch Sister Princess or Baby Princess, you have double digit siblings and they all call MC some variant of brother, but yeah its Onee / Onii, Imouto/Otouto ; and I think cousin Itoko (if im remembering school rumble correctly). Chan/Kun/Sama/Dono/San denote the level of relationship / level of respect. And then you even have stuff aneue which kind combines the two.