Tested with Harmony, Character Editor and Custom Pawn generation, no other mods enabled.

I get the following 3 errors;

Error 1:

Error while generating pawn. Rethrowing. Exception: System.NullReferenceException: Object reference not set to an instance of an object
at RimWorld.PawnRelationWorker_Sibling.CreateRelation (Verse.Pawn generated, Verse.Pawn other, Verse.PawnGenerationRequest& request) [0x000bc] in <95de19971c5d40878d8742747904cdcd>:0
at Verse.PawnGenerator.GeneratePawnRelations (Verse.Pawn pawn, Verse.PawnGenerationRequest& request) [0x0012f] in <95de19971c5d40878d8742747904cdcd>:0
at Verse.PawnGenerator.TryGenerateNewPawnInternal (Verse.PawnGenerationRequest& request, System.String& error, System.Boolean ignoreScenarioRequirements, System.Boolean ignoreValidator) [0x00366] in <95de19971c5d40878d8742747904cdcd>:0
at Verse.PawnGenerator.GenerateNewPawnInternal (Verse.PawnGenerationRequest& request) [0x00094] in <95de19971c5d40878d8742747904cdcd>:0
at (wrapper dynamic-method) Verse.PawnGenerator.Verse.PawnGenerator.GenerateOrRedressPawnInternal_Patch1(Verse.PawnGenerationRequest)
at Verse.PawnGenerator.GeneratePawn (Verse.PawnGenerationRequest request) [0x00007] in <95de19971c5d40878d8742747904cdcd>:0
UnityEngine.StackTraceUtility:ExtractStackTrace ()
Verse.Log:Error (string)
Verse.PawnGenerator:GeneratePawn (Verse.PawnGenerationRequest)
Verse.StartingPawnUtility:NewGeneratedStartingPawn (int)
Verse.StartingPawnUtility:RegenerateStartingPawnInPlace (int)
Verse.StartingPawnUtility:RandomizeInPlace (Verse.Pawn)
RimWorld.Page_ConfigureStartingPawns:RandomizeCurPawn ()
RimWorld.Page_ConfigureStartingPawns:<DrawPortraitArea>b__24_0 ()
RimWorld.CharacterCardUtility:DrawCharacterCard (UnityEngine.Rect,Verse.Pawn,System.Action,UnityEngine.Rect,bool)
RimWorld.Page_ConfigureStartingPawns:DrawPortraitArea (UnityEngine.Rect)
(wrapper dynamic-method) RimWorld.Page_ConfigureStartingPawns:RimWorld.Page_ConfigureStartingPawns.DoWindowContents_Patch1 (RimWorld.Page_ConfigureStartingPawns,UnityEngine.Rect)
Verse.Window:InnerWindowOnGUI (int)
UnityEngine.GUI:CallWindowDelegate (UnityEngine.GUI/WindowFunction,int,int,UnityEngine.GUISkin,int,single,single,UnityEngine.GUIStyle)


Error 2:

There was an exception thrown by the PawnGenerator during generating a starting pawn. Trying one more time...
Exception: System.NullReferenceException: Object reference not set to an instance of an object
at RimWorld.PawnRelationWorker_Sibling.CreateRelation (Verse.Pawn generated, Verse.Pawn other, Verse.PawnGenerationRequest& request) [0x000bc] in <95de19971c5d40878d8742747904cdcd>:0
at Verse.PawnGenerator.GeneratePawnRelations (Verse.Pawn pawn, Verse.PawnGenerationRequest& request) [0x0012f] in <95de19971c5d40878d8742747904cdcd>:0
at Verse.PawnGenerator.TryGenerateNewPawnInternal (Verse.PawnGenerationRequest& request, System.String& error, System.Boolean ignoreScenarioRequirements, System.Boolean ignoreValidator) [0x00366] in <95de19971c5d40878d8742747904cdcd>:0
at Verse.PawnGenerator.GenerateNewPawnInternal (Verse.PawnGenerationRequest& request) [0x00094] in <95de19971c5d40878d8742747904cdcd>:0
at (wrapper dynamic-method) Verse.PawnGenerator.Verse.PawnGenerator.GenerateOrRedressPawnInternal_Patch1(Verse.PawnGenerationRequest)
at Verse.PawnGenerator.GeneratePawn (Verse.PawnGenerationRequest request) [0x00172] in <95de19971c5d40878d8742747904cdcd>:0
at Verse.StartingPawnUtility.NewGeneratedStartingPawn (System.Int32 index) [0x00014] in <95de19971c5d40878d8742747904cdcd>:0
UnityEngine.StackTraceUtility:ExtractStackTrace ()
Verse.Log:Error (string)
Verse.StartingPawnUtility:NewGeneratedStartingPawn (int)
Verse.StartingPawnUtility:RegenerateStartingPawnInPlace (int)
Verse.StartingPawnUtility:RandomizeInPlace (Verse.Pawn)
RimWorld.Page_ConfigureStartingPawns:RandomizeCurPawn ()
RimWorld.Page_ConfigureStartingPawns:<DrawPortraitArea>b__24_0 ()
RimWorld.CharacterCardUtility:DrawCharacterCard (UnityEngine.Rect,Verse.Pawn,System.Action,UnityEngine.Rect,bool)
RimWorld.Page_ConfigureStartingPawns:DrawPortraitArea (UnityEngine.Rect)
(wrapper dynamic-method) RimWorld.Page_ConfigureStartingPawns:RimWorld.Page_ConfigureStartingPawns.DoWindowContents_Patch1 (RimWorld.Page_ConfigureStartingPawns,UnityEngine.Rect)
Verse.Window:InnerWindowOnGUI (int)
UnityEngine.GUI:CallWindowDelegate (UnityEngine.GUI/WindowFunction,int,int,UnityEngine.GUISkin,int,single,single,UnityEngine.GUIStyle)

Error 3 that kills the UI:

Exception filling window for RimWorld.Page_ConfigureStartingPawns: System.NullReferenceException: Object reference not set to an instance of an object
at RimWorld.Page_ConfigureStartingPawns.get_StartingPawnsAllBabies () [0x00018] in <95de19971c5d40878d8742747904cdcd>:0
at RimWorld.Page_ConfigureStartingPawns.get_ExtraCanDoNextReport () [0x00007] in <95de19971c5d40878d8742747904cdcd>:0
at (wrapper dynamic-method) RimWorld.Page_ConfigureStartingPawns.RimWorld.Page_ConfigureStartingPawns.DoWindowContents_Patch1(RimWorld.Page_ConfigureStartingPawns,UnityEngine.Rect)
at Verse.Window.InnerWindowOnGUI (System.Int32 x) [0x001d3] in <95de19971c5d40878d8742747904cdcd>:0
UnityEngine.StackTraceUtility:ExtractStackTrace ()
Verse.Log:Error (string)
Verse.Window:InnerWindowOnGUI (int)
UnityEngine.GUI:CallWindowDelegate (UnityEngine.GUI/WindowFunction,int,int,UnityEngine.GUISkin,int,single,single,UnityEngine.GUIStyle)

To recreate, enable the 3 mods, pick "The Sanguophage" start option, make a world and enter the character editor then press randomize until it errors out.