Absolutely they do! Assuming one or both knows something, I find it disgraceful they haven’t come forward to ease the pain of their own daughter. They need forceful separate questioning and time alone with the parents verbally ripping into them IMO. The gently gently approach doesn’t seem to have worked (I’m thinking of Jess and Josh’s carefully worded statement recently appealing for information).
This is a very frustrating case, but IMO, no assumptions can be made about whether LE has been gentle or harsh. If LE knows no more than I do, then it is super-harsh to claim they have a suspect in particular. (I think it is obvious enough to say without being unfair that clearly someone on the station did something to Gus, and it's fair to conclude that at the very least hiding Gus was deliberate. But that is not the same as saying we think we know which person did something that is a major crime.)
In addition, we do not know the parents' motivations behind their statement, or that it is intended to apply gentle pressure on the grandparents. That is an inference by outsiders, and for what ever it's worth, it's not my inference. I think the message for LE, and it was "Don't try to separate us, or turn us against each other during your investigation."
As for "forceful questioning," what do you mean? Water boarding? What will that achieve?
MOO
Edited to add: I think, reading between the lines of some posts, many people believe that Josh knew all along the station was not a safe place for his children. (But yet, they lived there, and he lived far away. That is not consistent with the reports of his deep concern for his children.)
A lot of sleuthers seem to conclude that Jess, too, knows that something bad happened, but has not been able to give information to LE to prove it. I doubt this very much, because if she had a feeling, I find it very hard to believe that she was not able to give LE directional information about where Gus might be, as she would have had much more recent locations for her parents and the perimeter would be smaller. The exception would be if she said something shocking like, "I haven't actually seen Gus myself since Sept 26," or the like. But...
If Jess had not seen Gus in longer than is implied by the released time line information, I don't get the Jess and Josh message of unity. Josh would be furious at Jess. Even though he apparently did the same, he'd probably blame Jess for letting Gus be in an unsafe caretaking situation. There would be no, "We are united in grief..." message. I tend to highly doubt that Josh had a unsuperficial reason for his tensions with Jess's family, because if it were really about substantive issues, a responsible parent would take action, not bail out. But if, in fact, he had a good reason to fear the station, Jess insisted on living there anyway, and then the worst happened, why would Josh be "united" with Jess now?
MOO