Rather late on this thread
But I agree with the above, INFJ for Ted Hughes. Clearly an introvert. Displayed Extraverted Feeling - cuddly, warm, nice. Driven by Introverted Intuiton - sees patterns, meanings, depth.
His one time wife Sylvia Plath was INFP. INFJ/INFP is a classic pairing and explains why they felt so comfortable around each other. They both had their own things going on, independent, but could come together to connect very easily. May also explain why the relationship didnt hold together for long (to put it extremely mildly) - its more of a friend pairing than romantic, not enough balance or contrast.
Anyway Im going INFP for Plath because, again, clearly an Introvert. But her external side was less cuddly than Hughes. Quicker, sharp, a little cutting. Extraverted Intuition. Driven by a deeply rich inner emotional world of Introverted Feeling. Such a turbulent inner world that she couldnt handle it unfortunately, and wanted out.
Check these links to see the difference in their extroverted processes - Extraverted Feeling for Hughes, Extraverted Intuition for Plath.
YouTube
YouTube