Another reason for the importance of the three satwa Graha's relationship with Shukra is-

Surya is the 11th from the natural 7th House tula and so it is a friend to the 7th as the 11th is the house of friends.

Now the naisargika mitra of Surya are Mangala, Ketu, Guru, Chandra.

If these Mangala and Ketu or not totally favourable because, firstly they are tamas and secondly they tend to discourage marital felicity (natural 8th Lords) and so the rest three if anyhow connected with Shukra, then they are the best remedy for all matters of relationships.

In this Surya indicates Lalitha, Chandra indicates Annapoornaa and Guru indicates Saraswati.