Relationship tree

(ML's father) (Ml's mother)
Duke {died in accident} ---》 1st Duchess {Deceased}
| |
| |
/
2ndDuchess Yustaf (ML)
(FL's mom, divorced or widowed), ---> Ran ----
{died in accident} (FL, older than) |
| ( yustaf, ) |
| (from 1st marriage ) |

son {died in accident} 《{Step siblings,}》
(Don't know his name he was 《{not blood related}》
the only child born after the duke
and the 2nd duchess marriage)

SON is related to RAN and YUSTAF becuz he was born after the 2nd duchess marriage making him related to both FL and ML by blood and parents.