One name, two nicknames, three characters

So weird, conundrum. I’m writing a European medieval fantasy sort of thing, and the two main characters are grandsons of the [name_m]King[/name_m]. The younger one is a prince, the heir of the heir and about 14/15. His cousin is about 10 year older, a knight, but is the illegitimate son of a princess.

Both of them are named after their grandfather the king, and I want them to use different nicknames.

I want the nicknames to be as distinct as possible (not [name_m]Jim[/name_m] and [name_u]Jamie[/name_u] for [name_u]James[/name_u]), and preferably for them to not sound like they are immediately from the same name (a [name_u]Drew[/name_u] and an [name_u]Andy[/name_u] for [name_m]Andrew[/name_m]).

Basically something like [name_f]Margaret[/name_f], where one person would have the nickname [name_f]Daisy[/name_f], and another would have the nickname [name_f]Meg[/name_f].

[name_m]Jon[/name_m] and [name_m]Nathan[/name_m] for [name_m]Jonathan[/name_m]
[name_m]Bill[/name_m]/[name_m]Jelle[/name_m]/[name_m]Liam[/name_m]/Helmo for [name_m]William[/name_m]
[name_u]Misha[/name_u] and [name_f]El[/name_f] for [name_u]Michael[/name_u]
[name_u]Gus[/name_u] and Aku for [name_m]Augustus[/name_m]
[name_m]Al[/name_m]/[name_u]Sandy[/name_u]/[name_u]Lex[/name_u]/[name_m]Ander[/name_m] for [name_m]Alexander[/name_m]
[name_m]Lion[/name_m] and [name_m]Nardo[/name_m] for [name_m]Lennard[/name_m]

I think that’s really difficult to find, but though Wandarine has some great suggestions.

I would also add
[name_u]Sasha[/name_u] and Lek/[name_u]Lex[/name_u] for [name_m]Alexander[/name_m]
[name_m]Seb[/name_m] and Bast for [name_m]Sebastian[/name_m]
[name_u]Teddy[/name_u] and [name_u]Theo[/name_u] for [name_m]Theodore[/name_m]
[name_u]Teddy[/name_u] and [name_m]Ward[/name_m] for [name_m]Edward[/name_m]

I would also suggest maybe looking at names which have an meaning that could be a name itself.
[name_m]Arthur[/name_m] means bear, nicknamed [name_m]Bear[/name_m] and [name_m]Artie[/name_m]
[name_m]Corvin[/name_m] means raven, nicknamed [name_u]Raven[/name_u] and [name_m]Cor[/name_m]
[name_m]Phelan[/name_m] means ‘like a wolf’, nicknamed [name_m]Wolf[/name_m] and Phee.
[name_m]Lyall[/name_m] means wolf, nicknamed [name_m]Wolf[/name_m] and [name_m]Ly[/name_m].
[name_m]Viridian[/name_m] is a shade of green, nicknamed [name_f]Dian[/name_f] and [name_u]Green[/name_u].
[name_f]Sapphire[/name_f], nicknamed Saf and [name_u]Blue[/name_u].

You could also have one with a nickname related to the name, and the other have an unrelated nickname. If one has blue eyes, maybe they get called [name_u]Blue[/name_u]. If they are a good [name_m]Archer[/name_m], maybe they get called [name_m]Archer[/name_m].

[name_m]Frederick[/name_m] - [name_m]Erick[/name_m], [name_u]Red[/name_u], [name_m]Ed[/name_m], [name_u]Ricky[/name_u]
[name_m]Hubert[/name_m] - [name_m]Hugo[/name_m], [name_u]Bertie[/name_u], [name_m]Herbie[/name_m]
[name_m]Percival[/name_m] - [name_u]Percy[/name_u] and [name_m]Valiant[/name_m]
[name_m]Reginald[/name_m] -[name_m]Al[/name_m] and [name_u]Reggie[/name_u], Alder and [name_u]Red[/name_u]
[name_m]Bertrand[/name_m] - [name_m]Ben[/name_m] and [name_u]Andy[/name_u]

[name_m]Abraham[/name_m] - [name_m]Abe[/name_m], [name_u]Abie[/name_u], [name_m]Bram[/name_m], [name_m]Ham[/name_m]
[name_m]Alexander[/name_m] - [name_u]Alex[/name_u], [name_m]Alec[/name_m], [name_m]Axel[/name_m], [name_u]Lex[/name_u], [name_m]Xander[/name_m], [name_u]Sasha[/name_u], [name_u]Andy[/name_u], Skandar
[name_m]Alfred[/name_m] - [name_m]Al[/name_m], [name_u]Alfie[/name_u], [name_u]Freddie[/name_u], [name_u]Red[/name_u]
[name_m]Atticus[/name_m] - [name_f]Atti[/name_f], [name_u]Kit[/name_u], [name_m]Ace[/name_m]
[name_m]Augustus[/name_m] - [name_u]August[/name_u], [name_u]Gus[/name_u], [name_m]Augie[/name_m], [name_u]Asa[/name_u]
[name_m]Barnaby[/name_m] - [name_m]Barney[/name_m], [name_m]Barnes[/name_m], [name_u]Bo[/name_u], [name_m]Ben[/name_m], [name_m]Abe[/name_m], [name_u]Abie[/name_u], [name_u]Barry[/name_u], [name_m]Arnie[/name_m], [name_m]Bear[/name_m]
[name_m]Bartholomew[/name_m] - [name_m]Bat[/name_m], [name_m]Bart[/name_m], Tolly, Oli
[name_m]Benjamin[/name_m] - [name_m]Ben[/name_m], [name_m]Benji[/name_m], [name_u]Jamie[/name_u]
[name_m]Charles[/name_m] - [name_u]Charlie[/name_u], [name_m]Chuck[/name_m], [name_m]Chaz[/name_m], [name_m]Chip[/name_m], [name_m]Carl[/name_m], [name_u]Chase[/name_u]
[name_m]Christopher[/name_m] - [name_u]Chris[/name_u], [name_u]Kit[/name_u], [name_m]Topher[/name_m], Cip, [name_f]Roe[/name_f]
[name_m]Frederick[/name_m] - [name_m]Fred[/name_m], [name_m]Eddie[/name_m], [name_m]Fitz[/name_m], [name_m]Fritz[/name_m], [name_u]Red[/name_u], [name_m]Rick[/name_m]
[name_u]James[/name_u] - [name_u]Jamie[/name_u], [name_u]Jem[/name_u], [name_m]Jack[/name_m], [name_m]Jam[/name_m], [name_m]Jas[/name_m], [name_m]Jim[/name_m], [name_m]Jimmy[/name_m]
[name_m]Jeremiah[/name_m] - [name_u]Jem[/name_u], [name_u]Remy[/name_u], [name_f]Miah[/name_f], [name_f]Ria[/name_f]
[name_m]Nathaniel[/name_m] - [name_m]Nate[/name_m], [name_u]Nat[/name_u], [name_f]Nell[/name_f], [name_m]Nathan[/name_m], [name_m]Thad[/name_m], [name_m]Thaniel[/name_m], [name_m]Ian[/name_m]
[name_m]Sebastian[/name_m] - [name_m]Seb[/name_m], Bash, [name_m]Bastian[/name_m], [name_m]Baz[/name_m], [name_m]Ian[/name_m], [name_u]Ash[/name_u], [name_u]Sacha[/name_u]
[name_m]Theodore[/name_m] - [name_u]Theo[/name_u], [name_m]Thor[/name_m], [name_u]Teddy[/name_u], [name_m]Eddie[/name_m], [name_m]Todd[/name_m], [name_m]Dore[/name_m]

[name_m]Reginald[/name_m] could be [name_u]Reggie[/name_u] or [name_u]Red[/name_u], and [name_m]Leonard[/name_m] can be [name_m]Len[/name_m] or [name_m]Leo[/name_m]