4 Be it worthy of your race and royal seed,
Be it > [Let your love be] seed > children [as yet unborn]
5 Then I avow, by this most sacred head
avow > take a vow by this most sacred head > [by your most royal head; "by my head" is an oath: cf. 201.19:1]
6 Of my dear foster child, to ease your grief,
grief > pain
7 And win your will: therefore away do dread:
win > gain, achieve will > [that which you desire] away do > do away with
8 For death nor danger from your due relief
death > [neither death] due > fitting; merited