Blood Ties is a secondary quest in The Witcher 3: Wild Hunt and can be picked up by speaking to a noblewoman near the Nilfgaardian Army Group 'Center' Camp.
Walkthrough
Near the merchants in the camp is a noblewoman sitting under a makeshift tent and, on talking to her, she'll ask for Geralt's help as none of the soldiers there will tell her what happened to her son, Hrodeberth. When agreed to, she'll then suggest talking to the quartermaster, Tavar Eggebracht, so make your way over to talk to him.
You can either pay him 150 
or use Axii. As both choices give the exact same information, it's better to use Axii as it gives more 
. Eggebracht will then reveal that the boy and his group attempted to desert and some were caught and hanged while the others fled into the nearby swamps. However, he doesn't know if Hrodeberth was among those hanged or not.
Head to the spot northwest of the House of Respite and once you enter the search area, use your Witcher Senses to find some tracks near a dead horse and examine both, then follow the tracks, where you'll come across a body to examine but it's not Hrodeberth. Continue following the tracks, where you may run into some ghouls, before finding several hanged men, one of which has red hair. Examine this body, then after Geralt comments he needs definite proof it's him, use Witcher Senses to find the unsent letter just below the body.
Return to the mother who will ask for the truth and Geralt will reveal that he's dead. You can then choose to lie in how he died or tell her the truth in that he deserted. Regardless of choice, she'll thank the witcher and reward him for his efforts with the same amount of and payment.
Journal entry
- Near the Nilfgaardian camp Geralt ran into a noblewoman from far-off Nazair. She had journeyed to the front in search of her son, a soldier. The woman was worried because her son would write her often, but at some point had suddenly stopped. No one in the camp knew what had happened to him, but the woman did not believe they were truly ignorant. She offered Geralt a reward for discovering the truth.
- It turned out the noblewoman's son had decided to desert along with some other disgruntled soldiers. A search party had immediately been sent after them. Some were caught and killed, while others managed to escape. Sadly, the woman's son was among those hanged. When she learned this, she was overcome with grief. The letter Geralt had found on her son's body informed her how monstrous war can be and how hard it is to judge the actions of the soldiers taking part in it.
Objectives
- Talk to the quartermaster about the noblewoman's son.
- Find Hrodeberth's body using your Witcher Senses.
- Search the site for personal artifacts using your Witcher Senses.
- Return to the mother.
Bugs
- The letter doesn't disappear from your quest items after the quest ends (whether you tell her her son died in battle or that he deserted). The item code for the letter is 'mq1055_letters' if you want to remove it using console commands.
Notes
- Interestingly, if you reveal to the mother that her son deserted and was killed for it, she'll at first claim it's a lie until Geralt gives her the letter and she'll read it aloud. This letter apparently contains a lot more in writing than what's shown in the inventory screen.
- Even if you lie to the mother and say he died in battle, the journal entry will reflect as if you told her the truth.
- The son's name is spelled two different ways: in the subtitles it's spelled as "Hrodberth" but the objectives for the quest spell it "Hrodeberth".