For husbandry, more Nius? Pwease? You can pick between what did nius look like as a kit, more of Nius and younger Cary getting along because that melted my heart and I will never be recovering, or maybe an explanation of what exactly a lovebirding primarch entails because im not entirely sure where to even begin to try picturing that.
A little kitty Nius and Cary’s eighth birthday, where he was very concerned about the candle.
As for lovebirding, behaviours to look out for are inappropriate proximity, obsessive self grooming when the lovebird-ed is present, flared feathers (Sanguinius/Astartes or primarchs with feathers specifically), mating dances, excessive grooming of the lovebird-ed, nest building, resource hoarding and obsessive behaviour which may all may lead to attempts at inappropriate intimacy.
Many of these behaviours (disregarding inappropriate intimacy and obsessive self grooming) can also be displayed for more platonic pack-bonding behaviours, but the obsessive behaviours should be challenged and corrected as soon as they appear.