I'd imagine Hinoka is a decent mother for Siegbert, not the best but up there. Let's take a look.
Growth rates: Going with the (Mother+Child)/2 formula.
Sigbert
Growth Rates
Hp: 42, Str: 45, Mag: 10, Skl: 42, Spd: 45, Luck: 42, Def: 35, Res: 30
Modifiers
Str: 4, Mag: -1, Skl: -1, Spd: 1, Luck: 3, Def: 1, Res: 1
Looking at Siegbert's growth rates, he's most definitely his Hinoka's son in this case since their growth rates are almost identical. And with his modifiers he definitely outshines Xander in terms of stats but Siegfried is just that good. The -1 skill cap does hurt a little but nothing to truly worry about.
Classes he would get: We know he gets Cavalier and Wyvern Rider from his father. Hinoka would give him Pegasus Warrior.
This means Hinoka gives him these skills without worry about marriage/buddy seals: Swallow Strike, Eastern Heart, Rally Speed, Mirror Strike, Soar, Sun God.
The skills Hinoka can give to Siegbert from her reclass options - Remember only one of these skills can be given to Siegbert.
Lance Fighter tree: Defense Seal, Substitute, Speed Seal, Lancefaire, Breaking Sky, Flamboyant
Buddy sealed options-
Priestess tree (Sakura)- Miracle, Rally Luck, Magic Counter, Renewal, Rally Magic, Tomefaire
Bowman tree (Setsuna)- Skill +2, Prescient Victory, Raven Strike, Bowfaire
Not sure cases:
Wyvern Rider (Camilla)- A waste of a buddy seal since Siegbert will always have the Wyvern Rider tree.
Rod Knight (Azura)- Not sure if Azura give Hinoka the class if so: Demoiselle (Distinguished Son for Siegbert), Resistance +2, Battle Command, Rally Resistance, Servant's Joy, Tomebreaker
The main skills that stand out to me are Lancefaire, Breaking Sky, Miracle (due to Siegbert's higher luck cap in this pairing), Tomebreaker.
I'm not going into all the possiblities of Siegbert buddying/marrying second gen units. But based on what I see here, this is a decent pairing for Siegbert.